A Shanghai Airlines Boeing 737 with 149 passengers aboard was forced to make an emergency landing in south China’s Hainan island on Wednesday while on a scheduled flight from Shanghai to Phnom Penh, Cambodia.

The airline said a "mechanical failure" occurred at around 11:22 p.m. on flight FM 833 and the aircraft was forced to land at Meilan International Airport, Haikou.

An airline spokesman said an alarm light in the cockpit had alerted the crew to a problem with a fuel pump.

The passengers were alerted to the problem and were asked to stay calm, said the spokesman.

None of the emergency equipment was used in the incident and all the passengers were safe and unharmed, he said.

The aircraft had left Shanghai at 7:40 p.m. and was scheduled to arrive at Phnom Penh at 12:45 a.m. on Thursday.

"After the emergency landing, the airline authorities ordered another aircraft be flown to Haikou to complete the flight, and provided the passengers with water and instant noodles," said the spokesman.

The replacement aircraft arrived at Haikou at 3:35 a.m. on Thursday, picked up all the passengers and took off at 6:28 a.m. It was scheduled to arrive at the Cambodian capital by 9 a.m..

Aviation authorities and the airline are investigating the cause of the mechanical failure.